苏北盆地高邮凹陷古近系戴南组滨浅湖沉积中的遗迹化石

苏北盆地高邮凹陷古近系戴南组滨浅湖沉积中动物遗迹化石共鉴定出6个遗迹属8个遗迹种，其中1个为未定种。包括Taenidium barretti、Taenidium satanassi、Beaconites coronus、Cystichnum curvativum、Palaeophycus isp.、Planolites montanus、Skolithos verticalis和Skolithos linearis等。这些遗迹化石主要是无脊椎动物的进食迹和居住迹，呈全浮痕或半浮痕保存。根据组合特征及沉积环境分析，可识别出两个遗迹化石组合:1）Taenidium—Beaconites遗迹组合，主要由具新月型回填纹构造的进食迹组成，反映了周期性干旱气候条件下的滨浅湖沉积环境；2）Skolithos linearis遗迹组合，主要由居住潜穴组成，代表了三角洲平原—前缘沉积环境。生物扰动根据扰动特点，可分为三种类型，即1）均一型，反映了湖平面缓慢上升之后较长时间保持稳定；2）增强型，反映了湖平面整体稳定条件下的小幅度快速上升，然后保持稳定和缓慢下降；3）复合型，反映了湖平面先缓慢上升，然后缓慢下降。三角洲平原-前缘分支河道沉积序列中遗迹化石的类型、丰度、分异度和扰动指数垂向上呈规律性的变化，结合其沉积学特征分析，可分为四个沉积单元，每个沉积单元的内部物理成因构造和生物成因构造明显不同。

Trace Fossils of Shore-shallow Lacustrine Dainan Formation (Paleogene) in Gaoyou Sag, Subei Basin, Jiangsu Province

The trace fossils in shore-shallow lacustine sediments in Dainan Formation,Paleogene in Gaoyou Sag,Subei Basin consist of at least 6 ichnogenera,8 ichnospecies,namely,Taenidium barrette,Taenidium satanassi, Beaconites coronus,Cystichnum curvativum,Palaeophycusisp.,Planolites montanus,Skolithos verticalis and Skolithos linearis.These trace fossils were mainly of Fodinichnia and Domichnia of invertebrates,and were preserved in full relief and epirelief.Based on the integrated analysis of assembage traits and paleoenvironments,two ichno-assemblages are recognized: 1)TaenidiumBeaconites assemblage,which is mainly of feeding burrows with crescent backfilled structures,and presents itself in shore-shallow lacustrine sediments under periodically arid climate;2)Skolithos linearis assemblage,which is mainly of dwelling burrows,and presents itself in delta plain-frontsediments.Based on analysis of bioturbation variation features,three bioturbation assemblages are identified: 1) homogeneous one,which indicates that the water level might rise slowly within little scope and then be stable for a relatively long time; 2) stronger upwards one,which indicates that the water levelwas generally stable and might rise within little scope,and then be stable,and fall finally;3) compound one,which indicates that the water level might rise slowly and then fall slowly.In a fan plain-front distributary channel sedimentary sequence,the genres,abundance,diversity of trace fossils and the bioturbation index exhibit regularity vertically.Based on analysis of sedimentology and ichnology,a distributary channel sequence can be divided into 4 sedimentary sets,and each set exhibits different physical and biologic structures.